Magnetic core



June 11, 1929. J FRANK 1,717,199

MAGNETIC CORE Filed Aug. 23, 1928 I nventor: John J. frank H isAttor'ney.

Patented June 11, 1929.

UNITED STATES JOHN J. FRANK, OF PITTSFIELD, MASSACHUSETTS, ASSIGNOR'TOGENERAL ELECTRIC PATENT. OFFICE."

COMPANY, A CORPORATION OF NEW YORK;

MAGNETIC CORE.

Application filed August 23, 1928. Serial No. 301,592.

My intention relates to magnetic cores for electrical inductionapparatus, such as trans formers, and is particularly applicable inconnection with very large apparatusot this general character. A welldesigned'magnetic core is built up of thin superposed layers orlaminations of magnetic material which are carefully annealed andinsulated from each other to prevent excessive hysteresis and eddycurrent losses. The layers or laminations, or at least some o'l. them,for very large cores are so wide that .it ditlicult to anneal themproperly and to handle them without injury while they are being shaped,during the annealing process and while they are being assembled. Thelaminations of a large core generally have bolt holes punched in themand are held together by bolts passing through these holes. The boltsinterfere with the easy handling of the wide laminations which are aptto be bent and injured as they are assembled over the bolts. The generalobject of the invention is to provide an improved arrangement oflaminations for large cores which may be easily annealed and assembled.

The invention will be better understood from the following descriptiontaken in conneetion with the accompanying drawing in which Fig. 1 is aView of a magnetic core having laminations arranged in accordance withthe invention and Fig. 2 is a View of three of the wide laminationsseparated from each other to show details.

Like reference characters indicate similar parts'in both figures of thedrawing.

The magnetic core shown in Fig. 1 of the drawing is of a type commonlyused in transformers and includes two laminated winding legs 10connected at their ends by laminated yokes 11. Each winding leg 10 isbuilt up of laminations of different widths, the narrower ones beingoutside so that the leg approximates a cylindrical. shape to fit insidethe windings which surround it in the completed transformer.

The narrower outside laminations 12 may not be too wide to anneal andhandle conveniently without danger of injury to them and these are shownin the drawing as being formed in the usual way, each comprising asingle magnetic sheet having a row of holes punched in it for the bolts13. The wider inside laminations 14, however, are each formed in twolongitudinal sections 15 and 16. Each lamination 14 has a central row ofbolt holes 17 corresponding in position and spacing to thebolt holes inthe narrower outside laminations 12. The joint between the two sections15 and 16 of each wide lamination 14 extends along one edge of its rowofbolt holes 17 which are formed as notches in the inner edge of thewider section 15 of the lamina tion. In some of the laminations, thejoint between the two sections 15 and 16 is at one side of the row ofbolt holes 17 and in the other lami nations this joint is at the otherside ot the bolt holes so that the positions of the wider and narrowersections of some of the laminations are reversed laterally from theirpositions in the other laminations as indicated in Fig. 2. The inneredges of the wider sections 15 of the laminations thus overlap betweenthe boltholes and are pressed tightly together and held in place by thebolts 13. The narrower sections 16 of the laminations are held tightlyin place between the adjacent wvider sections 15 on the same side of thebolts.

It is obvious that by forming each of the wide laminations 14 in twosections, they may ie more easily handled during the shaping andannealing processes and with considerablyless chance of injury to them.This feature also facilitates the handling of the laminations andreduces the chance of injury to them during the assembling operation asthey need not be lifted and dropped down around the bolts. In assemblingeach lamination, its

two sections may be laid upon the part of the 7 core already assembledand pushed together with the edges of the notches or holes 17surrounding the bolts.

The invention. has been explained by describing and illustrating aparticular form thereof, but it will. be apparent that various changesmay be made without departing from thescope of. the invention asdefined.

What I claim as new and desire to secure by Letters Patent ot the UnitedStates, is:

1. A magnetic core including superposed laminations, each of saidlaminations including two longitudinal sections, and the inner edge ofat least one of said sections having notches therein to provide boltholes.

2. A magnetic core including superposed laminat-ions, each laminationincluding two longitudinal sections of unequal widths, and the inneredge of at least one of the sections of each lamination having notchestherein to provide bolt holes.

3. A magnetic core including superposed laminations, each of saidlaminations including two longitudinal sections, the inner edge of atleast one of the sections of each lamination having notches therein toprovide bolt holes, and the width of one of the sections of eachlamination being greater than that of the other section by an amountsubstantially equal to the distance across one of said bolt holes.

4. A magnetic core including superposed laminations, each of saidlan'linatio-ns including two longitudinal sections, the inner edge of atleast one of the sections of each lamination having notches therein toprovide bolt holes, and some of said lamination sections at oppositesides of said bolt holes having their inner edges overlapped.

5. A magnetic core including superposed laminations, provided with a rowof bolt holes, each of said laminatious including two sections separatedby a joint near an edge of said row of bolt holes. I

6. A magnetic core lamination including two longitudinal sections, therebeing notches along the joint between said sections to provide boltholes.

In witness whereof, I have hereunto set my hand this 21st day of August,1928.

JOHN J. FRANK.

